From 68c3d97fd813ceadf41d765cda1bfe970322b633 Mon Sep 17 00:00:00 2001
From: moneroexamples <moneroexamples@tuta.io>
Date: Tue, 20 Jun 2017 09:00:55 +0800
Subject: [PATCH] checking if COMMAND_RPC_GET_ALT_BLOCKS_HASHES exists added

---
 src/rpccalls.cpp |  54 ----------------------
 src/rpccalls.h   | 116 +++++++++++++++++++++++++++++++++++++++++++++--
 src/tools.h      |   2 +-
 3 files changed, 114 insertions(+), 58 deletions(-)

diff --git a/src/rpccalls.cpp b/src/rpccalls.cpp
index 8f522f8..b366bb3 100644
--- a/src/rpccalls.cpp
+++ b/src/rpccalls.cpp
@@ -208,60 +208,6 @@ rpccalls::get_network_info(COMMAND_RPC_GET_INFO::response& response)
     return true;
 }
 
-bool
-rpccalls::get_alt_blocks(vector<string>& alt_blocks_hashes)
-{
-    bool r {false};
-
-    COMMAND_RPC_GET_ALT_BLOCKS_HASHES::request req;
-    COMMAND_RPC_GET_ALT_BLOCKS_HASHES::response resp;
-
-    {
-        std::lock_guard<std::mutex> guard(m_daemon_rpc_mutex);
-
-        if (!connect_to_monero_deamon())
-        {
-            cerr << "get_mempool: not connected to deamon" << endl;
-            return false;
-        }
-
-        r = epee::net_utils::invoke_http_json("/get_alt_blocks_hashes",
-                                              req, resp,
-                                              m_http_client);
-    }
-
-    string err;
-
-    if (r)
-    {
-        if (resp.status == CORE_RPC_STATUS_BUSY)
-        {
-            err = "daemon is busy. Please try again later.";
-        }
-        else if (resp.status != CORE_RPC_STATUS_OK)
-        {
-            err = "daemon rpc failed. Please try again later.";
-        }
-
-        if (!err.empty())
-        {
-            cerr << "Error connecting to Monero deamon due to "
-                 << err << endl;
-            return false;
-        }
-    }
-    else
-    {
-        cerr << "Error connecting to Monero deamon at "
-             << deamon_url << endl;
-        return false;
-    }
-
-    alt_blocks_hashes = resp.blks_hashes;
-
-    return true;
-}
-
 
 bool
 rpccalls::get_dynamic_per_kb_fee_estimate(
diff --git a/src/rpccalls.h b/src/rpccalls.h
index 560d9c4..596dc38 100644
--- a/src/rpccalls.h
+++ b/src/rpccalls.h
@@ -10,6 +10,38 @@
 
 #include <mutex>
 
+
+namespace
+{
+
+    // can be used to check if given class/struct exist
+    // from: https://stackoverflow.com/a/10722840/248823
+    template <typename T>
+    struct has_destructor
+    {
+        // has destructor
+        template <typename A>
+        static std::true_type test(decltype(declval<A>().~A()) *)
+        {
+            return std::true_type();
+        }
+
+        // no constructor
+        template <typename A>
+        static std::false_type test(...)
+        {
+            return std::false_type();
+        }
+
+        /* This will be either `std::true_type` or `std::false_type` */
+        typedef decltype(test<T>(0)) type;
+
+        static const bool value = type::value;
+    };
+
+}
+
+
 namespace xmreg
 {
 
@@ -17,6 +49,12 @@ using namespace cryptonote;
 using namespace crypto;
 using namespace std;
 
+// declare it. monero should provide definition for this,
+// but we need to have it declared as we are going to
+// check if its definition exist or not. depending on this
+// we decide what gets to be defined as
+// get_alt_blocks(vector<string>& alt_blocks_hashes);
+struct COMMAND_RPC_GET_ALT_BLOCKS_HASHES;
 
 class rpccalls
 {
@@ -52,15 +90,87 @@ public:
     bool
     get_network_info(COMMAND_RPC_GET_INFO::response& info);
 
-    bool
-    get_alt_blocks(vector<string>& alt_blocks_hashes);
-
     bool
     get_dynamic_per_kb_fee_estimate(
             uint64_t grace_blocks,
             uint64_t& fee,
             string& error_msg);
 
+
+    /**
+     * This must be in the header for now, as it will be tempalte function
+     *
+     * @param alt_blocks_hashes
+     * @return bool
+     */
+    template<typename T = COMMAND_RPC_GET_ALT_BLOCKS_HASHES>
+    typename enable_if<has_destructor<T>::value, bool>::type
+    get_alt_blocks(vector<string>& alt_blocks_hashes)
+    {
+        // definition of COMMAND_RPC_GET_ALT_BLOCKS_HASHES exist
+        // so perform rpc call to get this information
+
+        bool r {false};
+
+        typename T::request req;
+        typename T::response resp;
+
+        {
+            std::lock_guard<std::mutex> guard(m_daemon_rpc_mutex);
+
+            if (!connect_to_monero_deamon())
+            {
+                cerr << "get_mempool: not connected to deamon" << endl;
+                return false;
+            }
+
+            r = epee::net_utils::invoke_http_json("/get_alt_blocks_hashes",
+                                                  req, resp,
+                                                  m_http_client);
+        }
+
+        string err;
+
+        if (r)
+        {
+            if (resp.status == CORE_RPC_STATUS_BUSY)
+            {
+                err = "daemon is busy. Please try again later.";
+            }
+            else if (resp.status != CORE_RPC_STATUS_OK)
+            {
+                err = "daemon rpc failed. Please try again later.";
+            }
+
+            if (!err.empty())
+            {
+                cerr << "Error connecting to Monero deamon due to "
+                     << err << endl;
+                return false;
+            }
+        }
+        else
+        {
+            cerr << "Error connecting to Monero deamon at "
+                 << deamon_url << endl;
+            return false;
+        }
+
+        alt_blocks_hashes = resp.blks_hashes;
+
+        return true;
+    }
+
+    template<typename T = COMMAND_RPC_GET_ALT_BLOCKS_HASHES>
+    typename enable_if<!has_destructor<T>::value, bool>::type
+    get_alt_blocks(vector<string>& alt_blocks_hashes)
+    {
+        cerr << "COMMAND_RPC_GET_ALT_BLOCKS_HASHES does not exist!" << endl;
+        // definition of COMMAND_RPC_GET_ALT_BLOCKS_HASHES does NOT exist
+        // so dont do anything
+        return false;
+    }
+
 };
 
 
diff --git a/src/tools.h b/src/tools.h
index daed30b..9b0c354 100644
--- a/src/tools.h
+++ b/src/tools.h
@@ -30,7 +30,7 @@
 #include <vector>
 #include <iterator>
 #include <algorithm>
-
+#include <type_traits>
 
 
 /**